1. Field of the Invention
Various switches other than a horn switch are now fitted to a steering wheel with the progress in car electronics for motor cars. For instance, the switches for a speed controller, audio equipment, and the like, can be operated more easily and more safely if they can be fitted to the center portion of the steering wheel which is kept stationary independently of the revolution of the steering wheel.
When the switches are disposed at the center portion of the steering wheel, the present invention pertains to an improvement in, or relating to, a mechanism which keeps the switches under a nonrotary state at predetermined positions, though the steering switch can of course rotate when operated.
2. Description of the Prior Art
Japanese Utility Model Laid-Open No. 60053/1984 discloses a handle-top base fixing device which can keep always stationary a switch base disposed on the front surface of a steering wheel relative to a car body irrespective of the revolution of a handle. This device includes a first sun pulley fitted to the reverse surface of a switch base, a second sun pulley fitted to a fixing member such as a column in such a manner as to face the first sun pulley, first and second planetary pulleys disposed coaxially with each other on the front and reverse surfaces of handle spokes inserted between the first and second sun pulleys and timing belt streched between the first sun pulley and the first planetary pulley and between the second sun pulley and the second planetary pulley, respectively.
Since the switch base fixing device described above needs two sun pulleys, two planetary pulleys and timing belts streched between these sun and planetary pulleys, the device becomes unavoidably complicated in structure and its thickness becomes inevitably great.
In order to improve the mechanism described above, Japanese Utility Model Laid-Open No. 51250/1986 discloses a mechanism including an upper large pulley fitted to the reverse surface of a steering pad, a lower large pulley fitted to a fixing member such as a column in such a manner as to face the upper large pulley, a hub plate of a steering wheel interposed between these upper and lower large pulleys, small guide pulleys fitted to the front and reverse surfaces of the hub plate and a wire wound several turns on the upper and lower large pulleys and having both end portions thereof connected through the small pulleys. In this structure, too, the thickness of the mechanism becomes great because of the upper and lower large pulleys and the small guide pulleys.